The present invention relates to electrically powered vehicles, more particularly to vehicles in which drive motor elements, control circuits and power supply are contained within one or more vehicle wheels.
The above identified Pyntikov et al. and Maslov et al. applications describe the development of efficient battery powered electric motor drives that may be advantageously employed in vehicles and other environments. The applications address the challenges of attaining smooth operation over a wide speed range, while maintaining a high torque output capability at minimum power consumption. Electronic control of pulsed energization applied to motor windings, by precisely varying pulse width, duty cycle, and switched application of a battery source, provides a wide functional versatility and flexible management of motor characteristics.
While the complexity of electronic elements can be extensive and diverse, the need is recognized for a motor structural configuration in which the control elements that provide such operation are self-contained. Such a configuration should not be made at a sacrifice in performance of the motor flux producing structure within a given constituent of the motor. The Pyntikov et al. and Maslov et al. applications contemplate configurations in which the stator is formed of a plurality of individual power modules and corresponding core segments, each module comprising electrical control and drive elements supplied by a power source incorporated within the stator. Such parallel architecture provides relatively independently controlled functionality for each module. Performance of each module individually may be measured in situ during normal operation or by running more extensive, software controlled, diagnostic routines. Based on test results, a module can be automatically recalibrated, disconnected, or flagged for repair or replacement. Overall motor performance, determined by combining the characteristics of the independent modules, can be compared to original benchmarks to analyze various repair options for devising the minimum necessary action.
In environments in which portability and size are important factors, such as bicycles, tricycles, motorcycles and the like, a vehicle motor drive should advantageously provide ready accessibility to the various structural components for replacement of parts at a minimum of inconvenience. Smaller vehicles present additional challenges to incorporate motor controls, which can be sophisticated, motor structure and one or more power supplies within a limited available space. For example, a power source must be provided that has a sufficient capacity for satisfactory operation of a vehicle drive such as described above while satisfying rather severe space and weight requirements of small vehicles. The need exists for providing such a power source within the confines of the vehicle structure while also being unobtrusive to the user.
The present invention fulfills the above described needs, at least in part, by provision of an electrically powered vehicle, for example a bicycle, having a motor, controller, power supply and charger contained within a wheel compartment. A cylindrical stator frame is fixed on the wheel axle, with an inner surface of the stator frame defining a space for housing the power supply. A plurality of electromagnet stator segments are mounted on and distributed about an outer surface of the stator frame. A cylindrical rotor frame is coupled to the axle through bearings. An inner surface of the rotor frame supports a plurality of permanent magnets distributed about the surface and surrounding the stator segments to form a radial air gap therebetween. The outer surface of the rotor frame supports a tire that is mounted thereon via a supporting structure such as a bicycle spoke frame or that may be mounted thereon directly. The motor, power supply and motor control circuit may all be contained within a front or back wheel hub of a bicycle that is readily accessible. For particulars of various rotor and stator structural configurations and a motor control scheme for generating electromotive force, reference is made to the above-identified patent applications.
The power supply requirements are dependent upon vehicle variables, such as size and weight, as well as the particular motor structural configuration and desired operating characteristics. The power supply may comprise a plurality of standard battery cells, such as D-cells, which can be replaced easily when necessary with readily available cells. An advantage of such cells is that they are readily available, as are rechargeable batteries. With easy access, the batteries can be exchanged with other rechargeable batteries and stored for reuse later. With appropriate connection of the batteries to an external portion of the wheel, the batteries can be recharged in situ, without the need for taking apart the wheel.
A further advantage of the invention is that additional battery cells may be contained within storage space in a second wheel and coupled, via an electrical cable carried by the vehicle frame, to the motor drive in the first wheel. Provision of commonly available batteries in both wheels broadens the range of useful operating environments to include more rugged vehicles or multi-passenger vehicles. Depending on the particular design characteristics of the motor, the cells all may be connected in appropriate parallel and/or series/parallel configurations.
As an added feature, a switch may be provided in the cable circuit to permit selective connection of the cells in the second wheel to the motor and its controller. Smaller vehicles may not require the simultaneous connection of all the batteries at all times. During periods of light use or when the first wheel contains new or newly charged batteries, connection of the second wheel batteries may be opened by the switch, thereby conserving the power supply. These batteries may be switched into circuit during higher torque requirements, for example travel at a severe uphill gradient or when carrying an additional passenger and/or heavy loads. The batteries in the second wheel thus comprise a reserve power supply that can also be switched into circuit when the batteries in the first wheel indicate a loss of power after a period of use.
The reserve power supply can be contained in a front bicycle wheel, which can easily be removed from the vehicle without disturbing the rear wheel. Removal of the rear wheel is more cumbersome due to the added weight of the motor components and its interconnection with the bicycle chain. The front wheel batteries can be easily taken to a remote location where the batteries can be recharged or replaced. Replacement of the front wheel with the new or recharged power supply allows prolonged use of the vehicle so that attention to the rear wheel can be delayed to a more convenient time.
Yet another aspect of the invention is the provision of a motor, controller, charger and power supply in each of a plurality of wheels of the vehicle. This xe2x80x9call wheel drivexe2x80x9d functionality permits a greater range of control of the vehicle for better traction and torque distribution, and adds a level of redundancy to the drive system.
Additional advantages of the present invention will become readily apparent to those skilled in this art from the following detailed description, wherein only the preferred embodiment of the invention is shown and described, simply by way of illustration of the best mode contemplated of carrying out the invention. As will be realized, the invention is capable of other and different embodiments, and its several details are capable of modifications in various obvious respects, all without departing from the invention. Accordingly, the drawings and description are to be regarded as illustrative in nature, and not as restrictive.